Referring to FIGS. 1 and 2, a conventional circular saw with a movable saw arm is shown as represented by Chinese patent application No. 152478. Such a conventional circular saw has a base 12 which has a cutting groove 11 defined therein, a movable unit 13 pivotally connected to the base 12, and a saw arm 14 pivotally connected to the movable unit 13.
The movable unit 13 has a sliding frame 15 pivotally connected to the base 12, two movable sliding bars 16 both parallelly and intervally disposed on the sliding frame 15 relative to each other, and a sliding base 17 pivotally connected to the saw arm 14 and which is adapted for accommodating the sliding bars 16. The saw arm 14 has a driving motor 18 which is installed on the sliding base 17, and a saw blade 19 which is driven by the driving motor 18 and engageable with the cutting groove 11.
Such a conventional circular saw has many drawbacks. First of all, the entire load of the saw arm 14 and the sliding bars 16 are loaded on the sliding base 17 such that the saw arm 14 may swing vertically, thus influencing the precision of the cutting operation performed. This is because the saw arm 14 is driven by the sliding bars 16 to move further away from the sliding frame 15 due to the sliding bars 16 being both parallel to each other and disposed at an interval relative to each other. Moreover, stability of the saw arm 14 is poor when performing the cutting operation since the saw arm 14 wiggles, which may shorten the usable life of the circular saw.
Second, a structure of the sliding frame 15 has to be enhanced for supporting the saw arm 14 and the sliding bars 16 since the sliding base 17 is suspended above the base 12 with the support of the sliding frame 15. Additionally, the length of the sliding bars 16 have to be lengthened for maintaining the cutting distance at a certain specification, thereby increasing the overall manufacturing cost.
Third, a rear side of the base 12 has to reserve sufficient space for allowing the sliding base 17 to linearly slide when performing the cutting operation since the saw arm 14 is located on a distal end of the sliding base 17. Furthermore, operation of such a conventional circular saw requires adequate space since it is very large in size. The conventional circular saw also takes up a lot of space when storing or moving it.